Application of linear elastic and elastic-plastic fracture mechanics parameters to high-temperature fatigue crack growth is examined to determine which parameter provides a better correlation of crack growth data. It is concluded that the J-integral concept is applicable to fatigue, and methods of determination of J for both load-controlled and displacement-controlled fatigue are discussed. The J-integral parameter is shown to be better than the linear elastic parameter K in correlating fatigue crack growth, particularly so in materials that undergo metallurgical changes during test resulting in changes in flow properties. Application of the J-integral concept to time-dependent and combined cycle and time-dependent crack growth is discussed in detail.